Tunnel Stub Box

The 2004 FEIS/EIR-approved design includes a retained-cut structure, or U-wall, at the west end of the Caltrain railyard for trains to transition between the underground Fourth and Townsend Street Station and the at-grade alignment to the south. The proposed Tunnel Stub Box is a new below-grade train box stub, which would be built beneath the U-wall to accommodate future grade separations and expedite future arrival of below-grade Caltrain and high-speed trains.